how to enhance Kafka streaming Consumer rate ?

[? ?]

Hi:
I used kafka streaming for real time analysis.
and I put stream_thread_num same with partitions of topic
and set ConsumerConfig.max_poll_records =500
I use foreach  method only in this
but find with large records in kafka. the cosumer LAG is big some times and 
trigger kafka topic rebalance.
How to how to enhance Kafka streaming Consumer rate ?
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